9,10 - dihydro - 4h - pyrazolo(1&#39;,5&#39;:1,6)pyrido (3,4-b)indole - 2,3 - dicarboxylic acids and esters



9,10 DIHYDRO 4H PYRAZOLO[1,5':1,6]PYRIDO [3,4-b]IND-LE 2,3 DICARBOXYLIC ACIDS AND ESTERS Hans A. Wagner, Skokie, Ill., assignor to G. D. Searle &

Co., Chicago, 111., a corporation of Delaware No Drawing. Filed Nov. 9, 1967, Ser. No. 681,897 Int. Cl. C07d 57/00; A61k 27/00 US. Cl. 260-2955 15 Claims ABSTRACT OF THE DISCLOSURE Preparation of the captioned compounds and their valuable pharmacological properties, including pepsininhibiting and anti-ulcerogenic activities, are disclosed.

This invention relates to 9,10-dihydr0-4H-pyrazolo [1,5:1,6]pyrid0[3,4-b]indole-2,3-dicarboxylic acids and esters, and processes for the preparation thereof. More particularly, this invention provides new, useful, and unobvious chemical compounds of the formula CI11H211+1 wherein n repreesnts a positive integer less than 8.

The cycloalkyl radicals represented by Z are typified by cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and the cycloalkenyl radicals represented thereby are, specifically, those derived from the aforesaid cycloalkyl radicals by elimination of 2 hydrogens to give rise to an endocyclic double bond. Among the cycloalkyl and cycloalkenyl radicals represented by Z, the cyclohexyl and A A or A cyclohexyli.e., cyclohexenyl-groupings are preferred.

The aralkyl radicals represented by Z are preferably those comprising a methyl grouping substituted by phenyl wherein a second phenyl or a lower alkyl grouping can also be substituted. Illustrative of such radicals are benzyl, a-methylbenzyl, a-ethylbenzyl, a-isopropylbenzyl, diphenylmethyl, etc.

The optionally-substituted phenyl radicals represented by Z are preferably phenyl and phenyl substituted by a lower alkoxy grouping or halogen. Those skilled in the art will recognize that lower alkoxy groupings have the formula -O-lower alkyl wherein lower alkyl is defined as before. The halogens embraced by Z are most desirably those of atomic number greater than 9 and less than 53-i.e., chlorine and bromine. Positioning of the lower alkoxy or halo substituent about the benzene ring is not critical, 0-, m-, and p-substituted phenyl groupings alike being contemplated.

Inasmuch as there is at least 1 asymmetric carbon atom present in each of the compounds of this invention, the compounds exist both as racemates and the stereochemically homogeneous isomers which compose them.

tates Patent 0 Compounds in which 2 asymmetric carbon atoms are present, such as the products of Example 7 hereinafter, commonly occur as mixtures of racemates separable, as illustrated, by fractional crystallization.

The compounds to which this invention relates are useful by reason of their valuable pharmacological properties. Thus, for example, they are pepsin-inhibiting and anti-ulcerogenic. The instant compounds are further useful in that they inhibit dicotyledenous seed germination.

The pepsin-inhibiting utility of the compounds of this invention is evident from the results of a standardized test for their effect on the proteolysis of hemoglobin by pepsin. The technique employed is a modification of that described by M. L. Anson in J. Gen. Physiol., 22, 79 (1938), and depends upon the fact that the aforesaid proteolysis results in liberation of peptides containing tyrosine and tryptophan units characterized by an absorption band in the ultraviolet spectrum at 275 m Absorption at this wavelength serves therefore as an index of the extent to which the proteolysis has occurred. Each test is carried out in 4 test tubes to which are added solutions, measured in ml., of hemoglobin, pepsin, compound, hydrochloric acid, and perchloric acid. The additions are made immediately before and immediately after simultaneous incubation at 37 in accordance with the schedule shown in Table I.

TABLE I The hemoglobin solution (HGB) is prepared by mixing 60 gm. of Hemoglobin Substrate PoWder (bovine) [Worthington Biochemical Corporation, Freehold, N.J.] with 2000 ml. of double distilled water, successively filtering and centrifuging the resultant slurry, adjusting the pH of the saturated solution thus separated to 2.0 with 6 N hydrochloric acid, and finally diluting with an equal volume of pH 2.0 hydrochloric acid, prepared as described below. The pepsin solution (PEP) is prepared by dissolving 4.0 mg. of 3X Crystallized Pepsin (hog) [Pentex, Incorporated, Kankakee, 111.] in 200 ml. of pH 2.0 hydrochloric acid and diluting 6.25 ml. of the resultant solution with a further quantity of pH 2.0 hydrochloric acid q.s. 25 ml. The compound solution (CPD) is prepared by mixing 5 mg. of compound with 5.0 ml. of pH 2.0 hydrochloric acid and filtering out any material which remains insoluble. The hydrochloric acid solution (HCl) is prepared by diluting concentrated hydrochloric acid to pH 2.0 with double distilled water. The perchloric acid is prepared by diluting concentrated perchloric acid with double distilled water q.s. 20% by volume.

When the additions after incubation have been completed, the contents of each tube is filtered to remove undigested protein precipitated by the perchloric acid (which also serves to inactivate the enzyme), 1 ml. of each filtrate is diluted with 10 ml. of pH 5 sodium acetate butler, and the resultant solutions are subjected to UV spectrophotometric analyses whereby the absorptions at 275 m are determined. Among the 4 values thus obtained for each compound tested, those derivingfrom tube Nos. 1 and 2 serve as controls, being representative of absorption due to peptides produced by incubation of uninhibited enzyme and substrate superimposed upon absorption due to compound itself, whereas those deriving from tube Nos. 3 and 4so-called treats-represent absorption due to peptides produced by incubation of enzyme and substrate in the presence of compound,

TABLE II Product; Control Treat Conclusion 10 .390 .371 Pepsin-inhibiting. 3O .406 .378 Do. 80 .388 .372 Do.

Pepsin is known to play a causal role in the production of peptic ulcer.

The anti-ulcerogenic utility of the instant compounds hereinbefore specified is evident from the results of a standardized test for their capacity to inhibit the ulceration reported by Shay et al., Gastroenterology, 5, 43 (1945), to occur in rats subjected to fasting and pyloric ligation. In this test, male Charles River rats weighing 200-250 gm. and fasted 72 hr. prior to ligation are used. Immediately following ligation, the prescribed dose of compound, dissolved or suspended in 1.0 ml. of pH 2.0 hydrochloric acid, is intragastrically administered to each of a group of 6 animals. A like group of animals to which is identically and concurrently administered the acid alone serves as controls. Precisely 19 hr. later, the stomachs of surviving animals are excised and examined under X magnification. The number of ulcers occurring in the non-secretory portion of each stomach is counted in 4 groups according to size 2 mm., 2-4 mm., 4-8 mm., and 8 mm); and each rat receives a score, 2, which is a Weighted average of the logarithms of the ulcer counts in the several size groups determined by a formula found approximately optimal by discriminant function analysis to be z=20.00 log (N1+1)+0.22 log (N2+1) +4676 log (N3+1)+6.11 log (N4+1) where N N, are the observed ulcer counts of the increasing size groups. Since long-term studies in approximately 400 animals show that the average z value for controls is 96.2, with a standard error per group of 6 equal to 18.97, a decrease in the average 1 score for a given test group, relative to concurrent controls, amounting to 37.5 or more is significant (P5005); and a compound producing such a decrease is considered antiulcerogenic.

Preparation of the instant compounds proceeds by contacting an acetic acid suspension of an appropriate 1,2,3,4 tetrahydro- 9H-pyrido[3,4-b]indole-3-carboxylie acid NE [Z being defined as above] OOOH with cool aqueous sodium nitrite to give the corresponding Z-nitroso compound, which, upon heating with acetic anhydride, affords the corresponding meso-ionic didehydro 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo [3,4': 1,6] pyrido [3,4-b] indole ii N N 0 [Z being 1 Ql defined as before} The latter compound is heated with an appropriate dialkyl acetylenedicarboxylate in ethylene glycol diethyl ether [diethyl Cellosolve] to give the 9,10-dihydro-4H- pyrazolo[1',5':l,6]pyrido[3,4-b]indole 2,3-dicarb0xylic 4 acid ester hereof, from which the free acid is obtained by saponification with hot aqueous methanolic potassium carbonate.

The following examples describe in detail compounds illustrative of the present invention and methods which have been devised for the preparation thereof. However, the invention is not to be construed as limited thereby, either in spirit or in scope, since it will be apparent to those skilled in the art of organic synthesis that many modifications, both of materials and of methods, may be practiced without departing from the purpose and intent of this disclosure. Throughout the examples hereinafter set forth, temperatures are given in degrees centrigrade and relative amounts of materials in parts by weight, except as otherwise noted.

EXAMPLE 1 (A) 1,2,3,4-tetrahydro-2-nitroso-9H pyrido[3,4 b] indole-3-carboxylic acid-To a suspension of 650 parts of l,2,3,4-tetrahydro-9H pyrido[3,4-b]indo1e 3-carboxylic acid in 4000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 235 parts of sodium nitrite in 400 parts of water. Stirring is continued 15 minutes longer, whereupon the resultant solution is mixed with decolorizing charcoal and filtered through diatomaceous earth. The filtrate is poured into 25,000 parts of ice-cold water, precipitating a yellowish solid which is filtered ofi, washed with water, and dried in air. The product thus isolated is 1,2,3,4-tetrahydro-2-nitroso 9H pyrido[3,4b]indole-S-carboxylic acid melting at 176-178 with decomposition.

'(B) Meso-ionic didehydro 3a,4,'9,10-tetrahydro-IH, 3H-[1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4 bJindol 3- one.A suspension of 50 parts of 1,2,3,4-tetrahydro-2- nitroso-9H-pyrido[3,4-b]indole-3-carboxylic acid in 210 parts of acetic anhydride is stirred at 60-65 for 1 /2 hours, during which time solution occurs. The solution is allowed to cool to room temperature during 2 hours, resulting in the formation of a crystalline precipitate. The mixture is poured into 2500 parts of water, and stirring is thereupon resumed for 3 hours. Insoluble solids are filtered off, washed on the filter with water, dried in air, sl-urried in hot methanol, re-isolated by filtration, and washed on the filter with a mixture of cold methanol and ether to give meso-ionic didehydro 3a,4,9,10-tetrahydro-1H,3H [1,-2,3]oxadiazolo[3',4':1,6]pyrido[3,4 b] indol-ol-3-one melting at 247-250 with decomposition.

(C) Dimethyl 9,l0-dihydro-4H-pyrazolo[1,5':1,6]pyrido[3,4-b] indole-2,3-dicarboxylate.A suspension of 227 parts of meso-ionic didehydro 3a,4,9,10-tetrahydro-1H, 3H[l,2,3]oxadiazolo[3',4:1,6]pyrido[3,4 b]indol 3- one in a mixture of parts of dimethyl acetylenedicarboxylate with 1500 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 2 /2 hours. Carbon dioxide is liberated and solution occurs in process. The solution is allowed to stand at room temperatures overnight, whereupon precipitation occurs. The precipitate, filtered off and recrystallized from acetone, affords dimethyl 9,10-dihydro-4H-pyrazolo[1,5: 1,6] pyrido[ 3,4- b]indole-2,3-dic arboxylate melting at 253-255 The product has the formula N -oooora -oooorn EXAMPLEZ 9,10-dihydro 4H pyrazolo[1',5': l,6]pyrido[3,4-b] indole-2,3-dicarboxylic acid.To a suspension of 65 parts of dimethyl 9,l0-dihydro-4H-pyrazolo[l',5:1,6]pyrido [3,4-b]indole-2,3-dicarboxylate in 1000 parts of methanol is added a solution of 60 parts of potassium carbonate in 250 parts of water. The resultant mixture is heated at the boiling point under reflux for 4 hours,

EXAMPLE 3 (A) 1,2,3,4-tetrahydro 1 methyl-2 nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid.Substitution of 690 parts of 1,2,3,4-tetrahydro-1-methyl-9H-pyrido[3,4- b]indole-3-carboxylic acid for the 1,2,3,4-tetrahydro-9H- pyrido[3,4-b]indole-3-carboxylic acid called for in Example 1A affords, by the procedure there detailed, 1,2,3,4- tetrahydro-l-methyl-2-nitroso-9H pyrido[3,4-b]indole-3- carboxylic acid melting at approximately 183-184 with decomposition.

(B) Meso-ionic didehydro 3a,4,9,10-tetrahydro-l0- methyl 1H,3H [l,2,3]oxadiazolo[3',4:l,6]pyrido[3, 4-b]indol-3-one.Substitution of 53 parts of 1,2,3,4-tetrahydro-1-methyl-2-nitroso-9H pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4-tetrahydro-2-nitroso-9H- pyrido-[3,4-b]indole-3-carboxylic acid called for in Example 1B affords, by the procedure there detailed, mesoionic didehydro 3a,4,9,lO-tetrahydro-lO-methyl-1H,3H- [1,2,3]oxadiazolo[3,4:l,6]pyrido[3,4 b]indol 3-one. The product decomposes at approximately 250 without melting.

(C) Dimethyl 9,10-dihydro--methyl-4H-pyrazolo[ 1, 5 1,6] pyrido 3,4-b] indole-2,3 dicarb oxylate.Substitution of 180 parts of meso-ionic didehydro 3a,4,9,10-tetrahydro-10 methyl 1H,3H [1,2,3]oxadiazolo[3',4:l, 6]pyrido[3,4-b]indol-3-one and 110 parts of dimethyl acetylenedicarboxylate for the 227 parts of meso-ionic didehydro 3a,4,9,10-tetrahydro 1H,3H[l,2,3]oxadiazolo [3,4':1,6]pyrido[3,4-b1indol-3-one and 155 parts of dimethyl acetylenedicarboxylate, respectively, called for in Example 1C affords, by the procedure there detailed, dimethyl 9,10-dihydro-10 methyl-4H pyrazolo[1,5:1, 6]pyrido[3,4-b]indole-2,3-dicarboxylate melting at approximately 230-231. The product has the formula COOCH COOCHa EXAMPLE 4 EXAMPLE 5 (A) 1 cyclohexyl 1,2,3,4 tetrahydro 9H pyrido- [3,4 b]indole 3 carboxylic acid.To a solution of 817 parts of L-tryptophan in a mixture of parts of 96% sulfuric acid and 5000 parts of water is added a solution of 493 parts of cyclohexanecarboxaldehyde in 5000 parts of ethanol. The resultant solution is heated at the boiling point under reflux in a nitrogen atmosphere for 17 hours, whereupon 4000 parts of concentrated ammonium hydroxide followed by 20 parts of decolorizing charcoal is slowly introduced. Heating at the boiling point under reflux is resumed for 10 minutes, at which point the mixture is filtered hot. The filtrate is diluted with 2000 parts of concentrated ammonium hydroxide and allowed to cool. The crystalline precipitate thrown down is l-cyclohexyl 1,2,3,4 tetrahydro 9H pyrido[3,4 b]indole- 3-carboxylic acid which, filtered off, washed Well with water, and dried in air, melts at 202204.

(B) 1 cyclohexyl 1,2,3,4 tetrahydro 2 nitroso- 9H pyrido[3,4 b]indole 3 carboxylic acid.To a suspension of 463 parts of l-cyclohexyl-1,2,3,4-tetrahydro- 9H-pyrido[3,4-b]indole-3-carboxylic acid in 3000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 117 parts of sodium nitrite in 300 parts of water. Stirring is continued 15 minutes longer, whereupon the resultant solution is treated with decolorizing charcoal and filtered. The filtrate is poured into 20,000 parts of icecold water, precipitating a yellowish solid which is filtered off, Washed with water, and dried in air. The product thus isolated is l-cyclohexyl-1,2,3,4-tetrahydro 2 nitroso- 9H-pyrido [3 ,4-b indole-3-carboxylic acid.

(C) Meso ionic didehydro 10 cyclohexyl 3a,4, 9,10 tetrahydro 1H,3H [1,2,3]0xadiazolo[3,4: 1,6]- pyrido[3,4-b]ind0l-3-one.-A solution of 43 parts of 1-cyclohexyl-1,2,3,4-tetrahydro 2 nitroso 9H pyrido[3,4- b]indole-3-carboxylic acid in 270 parts of acetic anhydride is heated to 50 with stirring, whereupon heating is dis continued While stirring is maintained for 2 hours longer. The resultant mixture is poured into 2000 parts of water. The mixture thus obtained is stirred for 3 hours, whereupon insoluble solids are filtered off, washed with water, dried in air, and further Washed by slurrying in hot methanol. The resultant product is meso-ionic didehydro 10- cyclohexyl 3a,4,9,l0 tetrahydro 1H,3H [1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4 b]indol 3 one melting (D) Dimethyl 1O cyclohexyl 9,10 dihydro 4H- pyrazolo[1,5': l,6]pyrido[3,4 b]indole 2,3 dicarxoylate.-A suspension of 232 parts of meso-ionic didehydro 10 cyclohexyl 3a,4,9,10 tetrahydro 1H,3H [1,2,3]- oxadiazolo[3',4:1,6]pyrido[3,4 b]indol 3 one in a mixture of 116 parts of dimethyl acetylenedicarboxylate with 2000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 5 hours. Solvent is removed from the resultant solution by vacuum distillation. The residue is chromatographed on silica gel, using benzene and ethyl acetate as developing solvents. From an eluate comprising 20% ethyl acetate in benzene, on evaporation of solvent, dimethyl 10-cyclohexyl-9,10-dihydro-4H- pyrazolo[1,5:1,6]pyrido[3,4 b]indole 2,3 dicarboxylate is obtained as the residue. The product has the formula EXAMPLE 6 (A) 1 (3 cyclohexenyl) 1,2,3,4 tetrahydro 9H- pyrido[3,4 b]indole 3 carboxylic acid-Substitution of 484 parts of 3-cyclohexene-1-carboxaldehyde for the cyclohexanecarboxaldehyde called for in Example A affords, by the procedure there detailed, 1-(3-cyclohexenyl) 1,2,3,4-tetrahydro-9H-pyrido[3,4 b]indo1e 3 carboxylic acid melting at 193-l95 with decomposition.

(B) 1 (3 cyclohexenyl) 1,2,3,4 tetrahydro 2- nitroso-9H-pyrido[3,4 b]indole 3 carboxylic acid. Substitution of 460 parts of 1-(3-cyclohexenyl)-1,2,3,4- tetrahydro 9H pyrido[3,4 b]indole 3 carboxylic acid for the 1 cyclohexyl 1,2,3,4 tetrahydro 9H- pyrido[3,4-b]indole-3-carboxylic acid called for in Example SB affords, by the procedure there detailed, 1-(3- cyclohexenyl) 1,2,3,4 tetrahydro 2 nitroso 9H- pyrido[3,4-b]indole-3-carboxylic acid.

(C) Meso ionic didehydro (3 cyclohexenyl)- 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo[3,4: 1,6] pyrido[3,4-b]indol-3-one.Substitution of 43 parts of 1 (3 cyclohexenyl) 1,2,3,4 tetrahydro 2 nitroso- 9H pyrido[3,4 b]indole 3 carboxylic acid for the 1 cyclohexyl 1,2,3,4 tetrahydro 2 nitroso 9H- pyrido[3,4 b]indole 3 carboxylic acid called for in Example 5C aflords, by the procedure there detailed, meso ionic didehydro 10-(3-cyclohexenyl) 3a,4,9,10- tetrahydro 1H,3H [1,2,3]oxadiazolo[3',4':1,6]pyrido- [3,4-b]indol-3-one melting at 216-218 with decomposition.

(D) Dimethyl 10 (3-cyclohexenyl) 9,10 dihydro- 4H pyrazolo[1',5:1,6]pyrido[3,4-b]indole 2,3 dicarboxy1ate.Substitution of 230 parts of meso-ionic didehydro 10 (3-cyclohexenyl) 3a,4,9,10 tetrahydro- 1H,3H [1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4-b]indol- 3-one for the meso-ionic didehydro 10- cyclohexyl- 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo[3, 4': 1,6] pyrido[3,4-b]indol-3-one called for in Example 5D affords, by the procedure there detailed, dimethyl 10-(3- cyclohexenyl) 9,10 dihydro 4H pyrazolo[1',5':1,6] pyrido[3,4-b]indole 2,3 dicarboxylate which, recrystallized from a mixture of acetone and n-pentane, melts at 186-188. The product has the formula EXAMPLE 7 10 (3-cyclohexenyl) 9,10 dihydro 4H pyrazolo [1,5':1,6]pyrido[3,4-b]indole 2,3 dicarboxylic acid.- A mixture of 81 parts of dimethyl 10-(3-cyclohexenyl)- 9,10 dihydro 4H pyrazolo[1',5:1,6]pyrido[3,4-b] indole-2,3-dicarboxylate and 60 parts of potassium carbonate with 900 parts of methanol and 300* parts of water is heated at the boiling point under reflux for 2 hours and then stirred into 7500 parts of water. The resultant mixture is let stand at around 5 overnight, at which point insoluble solids are filtered off, washed with ice-cold Water, dried in air, and extracted with volumes of boiling methanol. The material which remains insoluble is filtered out, consecutively washed with methanol and ether, and dried in air. The product thus isolated is 10-(3- cyclohexenyl) 9,10 dihydro 4H pyrazolo[1'5':1,6] pyrido[3,4-b]indole-2,3 dicarboxylic acid melting at 282-284, and having the formula -COOII The boiling extract is mixed with decolorizing charcoal, and the mixture is filtered. The filtrate is concentrated by distillation to the point of incipient precipitation, then allowed to cool to room temperature. The precipitate is thereupon filtered ofI' and dried in air. The product thus isolated is 10-(3-cyclohexenyl)-9,10-dihydro-4H-pyrazolo [1,5: 1,6] pyrido[3,4-b] indole-2,3-dicarboxylic acid melting at approximately 265-266".

EXAMPLE 8 (A) 1,2,3,4 tetrahydro 2 nitroso 1 phenyl 9H- pyrido[3,4-b]indole-3-carboxylic acid.To a suspension of 450 parts of 1,2,3,4-tetrahydro- 1 phenyl-9H-pyrido [3,4-b]indole-3-carboxylic acid in 2000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 127 parts of sodium nitrite in 200 parts of water. The resultant solution is mixed with decolorizing charcoal, the mixture is filtered, and the filtrate is poured into 20,000 parts of ice-cold water. The yellow solid which precipitates is filtered off, washed with cold water, and dried in air. The resultant product is 1,2,3,4-tetrahydro 2 nitroso 1 phenyl 9H pyrido[3,4-b]indole- B-carboxylic acid.

(B) Meso-ionic didehydro 3a,4,9,10 tetrahydro 10- phenyl 1H,3H [1,2,31oxadiazolo[3',4:1,6]pyrido [3,4-b]indol-3-one.--A solution of 35 parts of 1,2,3,4- tetrahydro 2 nitroso 1 phenyl 9H pyrido[3,4-b] indole-3-ca-rboxylic acid in 150 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution stirred for 2 hours and then poured into 1700 parts of water. The resultant mixture is stirred for 3 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and washed by trituration in hot methanol to give meso-ionic didehydro 3a,4,9,10- tetrahydro 10 phenyl 1H,3H [1,2,3]oxadiazolo [3,4':1,6]pyrido[3,4-b]indol-3-one melting at 228-230" with decomposition.

(C) Dimethyl 9,10 dihydro 10 phenyl 4H pyrazolo[1,5': 1,6] pyrido 3 ,4-b] indole-2,3-dicarboxylate. A suspension of 12 parts of meso-ionic didehydro 3a,4,9,10- tetrahydro 10 phenyl 1H,3H [1,2,3]oxadiazolo [3,4':1,6]pyrido[3,4-b]indol-3-one in a mixture of 10 parts of dimethyl acetylenedicarboxylate with parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 3 hours, whereupon solvent is removed by vacuum distillation and the residue chromatographed on silica gel. From an eluate comprising 10% ethyl acetate in benzene, on evaporation of solvent and recrystallization of the residue from a mixture of acetone and n-pentane, dimethyl 9,10-dihydro-10-phenyl-4H-pyrazolo[1,5':1,6]pyrido[3,4-b]indole 2,3 dicarboxylate melting at approximately 225-226 is obtained. The product has the formula OOOCH3 COOC-Ha parts of 1-(p-chlorophenyl)-1,2,3,4-tetrahydro-2-nitroso- 9H-pyrido[3,4-b]indole-3-carboxylic acid for the l,2,3,4- tetrahydro 2 nitroso 1 phenyl 9H pyrido[3,4-b] indole-3-carboxylic acid called for in Example 8B alfords, by the procedure there detailed, meso-ionic didehydro- 10 (p-chlorophenyl) 3a,4,9,l0 tetrahydro 1H,3H- [1,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indol 3 one melting at 224226 with decomposition.

(C) Dimethyl 10(p chlorophenyl)-9,10-dihydro-4H- pyrazolo[1,5: l,6]pyrido[3,4-b]indole 2,3 dicarboxylate.A suspension of 135 parts of meso-ionic didehydro 10 (p chlorophenyl) 3a,4,9,10 tetrahydro 1H,3H- [l,2,3]oxadiazolo[3',4:1,6]pyrido[3,4-b]indol-3-one in a mixture of 70 parts of dimethyl acetylenedicarboxylate with 1000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 3 hours, whereupon it is mixed with decolorizing charcoal and filtered. The filtrate is freed of solvent by vacuum distillation; and the residue is chromatographed on silica gel, using benzene and ethyl acetate as developing solvents. From an eluate comprising 10% ethyl acetate in benzene, on evaporation of solvent and recrystallization of the residue from a mixture of acetone and n-hexane, dimethyl 10-(pchlorophenyl) 9,10 dihydro 4H pyrazolo[l,5': 1,6] pyrido [3,4-b]indole-2,3-dicarboxylate melting at approximately 233-234 is obtained. The product has the formula -COOCH COOCH3 EXAMPLE 10 (A) l-(m bromophenyl) 1,2,3,4 tetrahydro-9H- pyrido [3,4-b indole-3-carboxylic acid.-Substitution of 814 parts of m-bromobenzaldehyde for the cyclohexanecarboxaldehyde called for in Example 5A affords, by the procedure there detailed, 1-(m-bromophenyl)-l,2,3,4- tetrahydro-9H-pyrido [3 ,4-b] indole-3-carboxy1ie acid.

(B) l-(m bromophenyl)-1,2,3,4-tetrahydro-2-nitroso- 9H-pyrido[3,4-b] indole-3-carboxylic acid.Substitution of 572 parts of 1-(m-bromophenyl)-1,2,3,4-tetrahydro- 9H-pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4- tetrahydro 1 phenyl 9H pyrido[3,4-b1indole-3-carboxylic acid called for in Example 8A alfords, by the procedure there detailed, 1-(m-bromophenyl)-1,2,3,4- tetrahydro 2 nitroso 9H pyrido[3,4-b]indole-3-carboxylic acid.

(C) Meso-ionic didehydro 10 (m bromopheny1)- 3a,4,9,10 tetrahydro-1H,3H,[l,2,3]oxadiazolo[3,4: 1,6] pyrido[3,4-b]indol-3-one.Substitution of 44 parts of 1-(m-bromophenyl)-l,2,3,4-tetrahydro 2 nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4- tetrahydro-Z-nitroso-l-phenyl 9H pyrido[3,4-b]indole- 3-carboxylic acid called for in Example 88 aifords, by the procedure there detailed, meso-ionic didehydro 10-(m-bromophenyl) 3a,4,9,10 tetrahydro 1H,.3H- [1,2,3 oxadiazolo [3 ,4:1,6]pyrido[3,4-b]ind0l-3-one.

(D) Dimethyl IO-(m-bromophenyl)-9,l0-dihydro-4H- pyrazolo[1,5':l,6]pyrido[3,4-b]indole 2,3 dicarboxylate.Substitution of parts of meso-ionic didehydro IO-(rn-bromophenyl) 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indol-3-one for the meso-ionic didehydro 3a,4,9,10-tetrahydr0-10-phenyl- 1H,3H [1,2,3]oxadiazolo[3',4:l,6]pyrido[3,4-b]indol- 3-one called for in Example 8C aifords, by the procedure there detailed, dimethyl 10-(m bromophenyl)-9,IO-dihydro 4H pyrazolo[1,5:1,6]pyrido[3,4-b]indole-2,3-dicarboxylate, having the formula EXAMPLE 1 1 (A) 1,2,3,4 tetrahydro 1 (p-methoxyphenyl)-2- nitroso-9H-pyrido 3 ,4-b indole-3-carboxylic acid-S ubstitution of 480 parts of 1,2,3,4-tetrahydro-l-(p-methoxyphenyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4-tetrahydro l phenyl-9H-pyrido[3,4-b]indole-3- carboxylic acid called for in Example 8A aifords, by the procedure there detailed, 1,2,3,4-tetrahydro-1-(p-methoxyphenyl) 2 nitroso 9H pyrido[3,4-b]indole-3-carboxylic acid.

(B) Meso-ionic didehydro 3a,4,9,10-tetrahydro-10-(p methoxyphenyl) 1H,3H [1,2,3]oxadiazolo[3,4:1,6] pyrido[3,4-b]indol-3-one.Substitution of 38 parts of 1,2,3,4-tetrahydro 1 (p-methoxyphenyl)-2-nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid for the 1,2,3,4- tetrahydro-Z-nitroso 1 phenyl-9H-pyrido[3,4-b]indole- 3-carboxylic acid called for in Example 8B affords, by the procedure there detailed, meso-ionic didehydro 3a,4,9,10 tetrahydro 10 (p-methoxyphenyl)-1H,3H- [1,2,3]oxadiazolo[3,4:1,6]pyrido[3,4-b]indole 3 one melting at l98200 with decomposition.

(C) Dimethyl 9,10 dihydro-10-(p-methoxyphenyl)- 4H-pyrazolo[1,5:1,6]pyrido[3,4-b]indole 2,3 dicarboxylate.Substitution of 13 parts of meso-ionic didehydro 3a,4,9,10 tetrahydro-IO-(p-methoxyphenyl)-1H,3H- [1,2,3]oxadiazolo[3,4':1,6]pyrido[3,4-b]indol-3-one for the meso-ionic didehydro 3a,4,9,lO-tetrahydro-lO-phenyl- 1H,3H [1,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b]indol- 3-one called for in Example 8C alfords, by the procedure there detailed, dimethyl 9,10 dihydro-lO-(p-methoxyphenyl) 4H pyrazolo[1,5:1,6]pyrido[3,4-b]indole- 2,3-dicarboxylate. The product has the formula -OOOCHa EXAMPLE 12 (A) 1 (0 ethoxyphenyl) 1,2,3,4 tetrahydro-9H- pyrido 3,4-b indole-3-carboxy1ic acid.Substitution of 660 parts of o-ethoxybenzaldehyde for the cyclohexanecarboxaldehyde called for in Example 5A affords, by the procedure there detailed, l-(o-ethoxyphenyl)-1,2,3,4- tetrahydro-9H-pyrido 3,4-b indole-3 -carboxylic acid.

(B) l-(o-ethoxyphenyl) l,2,3,4-tetrahydro 2-nitroso-9H-pyrido[3,4-b]ind0le 3-carb0xylic acidfiSubstitution of 518 parts of l-(o-ethoxyphenyl) 1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole 3-carboxylic acid for the 1,2,3,4-tetrahydro-l-phenyl 9H pyrid0[3,4-b]indole- 3-carboxylic acid called for in Example 8A affords, by the procedure there detailed, 1-(o-ethoxyphenyl)-1,2,3,4- tetrahydro 2-nitroso 9H-pyrido[3,4-b]indole 3-carboxylic acid.

(C) Meso ionic didehydro 10 (o-ethoxyphenyl)- 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo [3,4':1,6]pyrido[3,4 b]indol 3-one.-Substitution of 40 parts of 1 (o-ethoxyphenyl) 1,2,3,4-tetrahydro-2- nitroso-9H pyrido[3,4-b]indole 3-carhoxylic acid for the 1,2,3,4-tetrahydro 2-nitroso 1-phenyl-9H-pyrido [3,4-b]indole-3-carboxylic acid called for in Example 88 affords, by the procedure there detailed, meso-ionic didehydro 1O (o-ethoxyphenyl) 3a,4,9,10 tetrahydro- 1H,3H [l,2,3]oxadiazolo[3',4': 1,6] pyriodo[3,4-b1indol- 3-one.

(D) Dimethyl (o-ethoxyphenyl) 9,10-dihydro- 4H pyrazolo[1,5:1,6]pyrido[3,4-b]indole-2,3 dicarboxylate.Substitution of parts of meso-ionic didehydro lO-(o-ethoxyphenyl) 3a,4,9,l0-tetrahydro-1H,3H- [1,2,3]oxadiazolo[3,4:l,6]pyrido[3,4-b]indol 3 one for the meso-ionic didehydro 3a,4,9,10 tetrahydro-IO- phenyl 1H,3H [1,2,3]oxadiazolo[3',4:1,6]pyrido [3,4-b]indol-3-one called for in Example 8C affords, by the procedure there detailed, dimethyl 10-(o-ethoxyphenyl)-9,l0 dihydro 4H-pyrazolo[1,5:l,6]pyrido[3,4-b] indole-2,3-dicarboxylate. The product has the formula EXAMPLE 13 (A) l-benzyl 1,2,3,4 tetrahydro Z-nitroso 9H- pyrido[3,4-b]indole-3-carhoxylic acid.--To a suspension of 67 parts of l-benzyl 1,2,3,4 tetrahydro-9H-pyrido [3,4-b]indole-3-carboxylic acid in 400 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 17 parts of sodium nitrite in 35 parts of water. The resultant solution is mixed with decolorizing charcoal, the mixture is filtered through diatomaceous earth, and the filtrate is stirred into 300 parts of water. The yellow solid which precipitates is filtered off, Washed with water, .and dried in air. The product thus isolated is 1 benzyl-123,4 tetrahydro 2-nitroso 9H-pyrido [3,4-b] indole-3-carboxylic acid.

(B) Meso-ionic didehydro 10-benzyl 3a,4,9,10-tetrahydro 1H,3H-[l,2,3]oxadiazolo[3,4':l,6]pyrido[3,4-b] indole-3-one.-A solution of 65 parts of 1-benzy1-1,2,3,4- tetrahydro 2 nitroso 9H-pyrido[3,4,b]indole-3-carboxylic acid in 300 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution is stirred for 2 hours and then poured into 2500 parts of water. The resultant mixture is stirred for 4 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and recrystallized from methanol to give meso-ionic didehydro lO-benzyl 3a,4,9,10-tetrahydro 1H,3H [l,2,3]oxadiazolo[3',4':1,6]pyrido[3,4-b] indol-3-one melting at 2l5-217.

(C) Dimethyl 10-benzyl-9,l0 dihydro 4H-pyrazolo [1,5':1,6]pyrido[3,4-b]indole 2,3 dicarboxylate.A suspension of 22 parts of meso-ionic didehydro IO-benzyl- 3a,4,9,10 tetrahydro 1H,3H [1,2,3]oxadiazolo [3,4:1,6]pyrido[3,4- b]indol-3-one in a mixture of 11 parts of dimethyl acetylenedicarboxylate with 200 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 8 hours, whereupon solvent is removed by vacuum distillation and the residue recrystallized from a mixture of acetone and n-mntane to give dimethyl 10 benzyl 9,10 dihydro 4H pyrazolo [1,5':l,6]pyrido[3,4-b]indole 2,3 dicarboxylate melting at approximately 206-207. The product has the formula -cooout i --COOCII:

EXAMPLE 14 IO-benzyl 9,10 dihydro 4H pyrazolo[1',5':1,6] pyrido[3,4-b]indole 2,3-dicarboxylic acid.A mixture of parts of dimethyl l0benzyl-9,l0 dihydro-4H- pyrazolo[1',5:1,6]pyrido[3,4 b]indole 2,3 dicarboxylate with 1000 parts of methanol and a solution of 60 parts of potassium carbonate in 250 parts of water is heated at the boiling point under reflux for 4 hours and then poured into 5000 parts of cold water. The resultant solution is stirred with decolorizing charcoal and then filtered. The pH of the filtrate is adjusted to 4 with dilute hydrochloric acid, precipitating a crystalline solid which, filtered off, washed with water, dried in air, and recrystallized from methanol, atfords 10-benzyl-9,10-dihydro-4H- pyrazolo[1,5':1,6]pyrido[3,4-b]indole 2,3 dicarboxylic acid melting at 226-228". The product has the formula b LjTcooH COOH EXAMPLE 15 (A) 1,2,3,4-tetrahydro 1 (a-methylbenzyD-Z-nitroso-9H-pyrido[3,4-b]indole 3 carboxylic acid-To a suspension of 490 parts of 1,2,3,4-.tetrahydro-1-(amethylbenzyl)-9H-pyrido[3,4-b]indole 3 carboxylic acid in 3000 parts of acetic acid at 15 is added, during 30 minutes with stirring, a solution of 115 parts of sodium nitrite in 250 parts of water. The resultant solution is mixed with decolorizing charcoal, the mixture is filtered through diatomaceous earth, and the filtrate is stirred into 3000 parts of water The yellow solid which precipitates is filtered off, washed with water, and dried in air. The product thus isolated is 1,2,3,4-tetrahydro-1-(a-methylbenzyl)-2-nitroso-9H-pyrido[3,4-b]indole 3 carboxylic acid.

(B) Meso-ionic didehydro 3a,4,9,l0-tetrahydro-l0*(11- methylhenzyl) 1H,3H [l,2,3]oxadiazolo[3',4':1,6] pyrido[3,4-b]indol-3-one.-A solution of 65 parts of 1,2, 3,4-tetrahydro 1 (a-methylbenzy 2 nitroso-9H- pyrido[3,4-b]indole-3-carboxylic acid in 3000 parts of acetic anhydride is heated to 50, whereupon heating is discontinued and the solution is stirred for 2 hours and then poured into 2500 parts of water. The resultant mixture is stirred for 4 hours, at which point insoluble solids are filtered out, washed on the filter with water, dried in air, washed by slurrying in hot methanol, and again dried in air to give meso-ionic didehydro 3a,4,9,l0-tetrahydro 10 (a-methylbenzyl)-1H,3H-[l,2,3]oxadiazolo [3,4:1,6]pyrido[3,4-b1indol-3-one melting at approximately 237-2383 (C) Dimethyl 9,10-dihydro 10 (-a-methylbenzyD- 4H pyrazolo[1',5: l,6]pyrido[3,4-b]indole 2,3 dicarboxylate.A suspension of parts of meso-ionic didehydro 3a,4,9',10-tetrahydro 10 (a-methylbenzyn-lH, 3H-[1,2,3]oxadiazolo[3,4':1,6]pyrido[3,4-b]indol 3 H CH3 E N I N oooom -COOCHa EXAMPLE 16 9,10-dihydro (a-methylbenzyl)-4H-pyrazolo[1, 5:l,6]pyrido[3,4-b]indole 2,3 dicarboxylic acid. Substitution of 85 parts of dimethyl 9,10-dihydro-10-(amethylbenzyl) 4H pyrazolo[1',5:l,6-]pyrido[3,4-b] indole-2,3-dicarboxylate for the dimethyl 10-benzyl-9,l0- dihydro-4H-pyrazolo[1,5':l,6]pyrido[3,4-b]indole 2,3- dicarboxylate called for in Example 14 affords, by the procedure there detailed, 9,10-dihydro-10-(a-methyI- benzyl) 4H pyrazolo[1',5':1,6]pyrido[3,4-b]indole- 2,3-dicarboxylic acid melting at approximately 263264. The product has the formula HJICHa l N -COOH --COOH EXAMPLE 17 (A) l,2,3,4-tetrahydro 1 diphenylmethyl-9H-pyrido [3,4-b]indole-3-carboxylic acid-Substitution of 860 parts of diphenyl acetaldehyde for the cyclohexanecarboxaldehyde called for in Example 5A afiords, by the procedure there detailed, 1,2,3,4-tetrahydro-l-diphenylmethyl-9H-pyrido[3,4-b]indole 3 carboxylic acid melting at approximately 197-198.

(B) l,2,3,4-tetrahydro 2 nitroso-l-diphenylmethyl- 9H-pyrido[3,4-b]indole 3 carboxylic acid.--To a suspension of 50 parts of 1,2,3,4-tetrahydro-l-diphenylmethyl-9H-pyrido[3,4-b1indole 3 carboxylic acid in 350 parts of acetic acid at is added, during 30' minutes with stirring, a solution of 10 parts of SOdllllIIl nitrile in parts of water. Stirring is continued minutes longer, whereupon the resultant solution is treated with decolorizing charcoal and filtered. The filtrate is poured into 2000 parts of ice-cold water, precipitating a yellowish solid which is filtered oil, washed with cold water, and dried in air to give 1,2,3,4-tetrahydro-2-nitroso-l-diphenylmethyl- 9H-pyrido[3,4-b]indole-3-carboxylic acid melting at 189- 1911.

(C) Meso-ionic didehydro 3a,4,9,IO-tetrahydro-lO-diphenylmethyl 1H,3I-I [1,2,3]oxadiazolo[3,4':1,6,] pyrido[3,4-b]indol-3-one.A solution of 50 parts of 1,2, 3,4-tetrahydro-2-nitroso 1 diphenylmethyl-9H-pyrido [3,4-b]indole-3-carboxylic acid in 250 parts of acetic anhydride is heated to 55, whereupon precipitation occurs and heating is discontinued. The resultant solution is stirred for 2 hours, then poured into 2000 parts of water. Stirring is resumed for 3 hours, at which point insoluble solids are filtered out, washed with water, dried in air, and recrystallized from methanol to give meso-ionic didehydro 3a,4,9,l'0-tetrahydro 10 diphenylmethyl-IH, 3H-[1,2,3]oxadiazolo[3,4':1,6]pyrido[3,4-b-]indol 3 one melting at 243-245 with decomposition.

(D) Dimethyl 9,10-dihydro 10 diphenylmethyl-4H- pyrazolo[1,5':l,6]pyrido[3,4-b]indole 2,3 dicarboxylate.A suspension of 157 parts of meso-ionic didehydro 3a,4, 9,10-tetrahydro 10 diphenylmethyl-lH,3H-[1,2,3] oxadiazolo[3',4:1,6]pyrido[3,4-b]indol-3-one in a mixture of 67 parts of dimethyl acetylenedicarboxylate with 2000 parts of ethylene glycol diethyl ether is heated at the boiling point under reflux for 5 hours, whereupon solvent is removed by vacuum distillation and the residue recrystallized from a mixture of acetone and n-pentane to give dimethyl 9,lO-dihydro-10-diphenylmethyl-4H-pyrazolo[1,5:l,6]pyrido[3,4-b]indole 2,3 dicarboxylate melting at approximately 194-194.5. The product has the formula EXAMPLE 18 9.10 dihydro 10 diphenylmethyl 4H pyrazolo- [1,5: l,6]pyrido[3,4-b]indole 2,3 dicarboxylic acid.- To a suspension of 97 parts of dimethyl 9,10-dihydro-l0- diphenylmethyl 4H pyrazolo[1',5:l, 6]pyrido[3,4-b] indole-2,3-dicarboxylate in 1000 parts of methanol is added a solution of 60 parts of potassium carbonate in 250 parts of water. The resultant mixture is heated at the boiling point under reflux for 4 hours, then poured into 5000 parts of cold water. The solution which eventuates is stirred with decolorizing chorcoal and filtered. The pH of the filtrate is adjusted to 4 with dilute hydrochloric acid, inducing precipitation of a crystalline solid which is isolated by filtration, washed with water, dried in air and recrystallized from methanol to give 9,10-dihydro- 10 diphenylmethyl 4H pyrazolo[1',5':1,6]pyrido[3,4- b]indole-2,3-dicarboxylic acid melting at approximately 235-236. The product has the formula What is claimed is: 1. A compound of the formula wherein R represents hydrogen, lower alkyl, cyclohexyl, cyclohexenyl, phenyl, halophenyl in which the halo constituent has an atomic number greater than 9 and less than 53, (lower alkoxy)phenyl, benzyl, a-methylbenzyl, or diphenylmethyl and R represents hydrogen or lower alkyl.

2. A compound according to claim 1 wherein R represents lower alkyl.

3. A compound according to claim 1 wherein R represents hydrogen.

4. A compound according to claim 1 which is dimethyl 9,10 dihydro 4H pyrazolo[l',5:1,6]pyrido[3,4 b] indole-2,3-dicarboxylate.

5. A compound according to claim 1 wherein R represents methyl.

6. A compound according to claim 1 which is dimethyl 9,10 dihydro 10 methyl 4H pyrazolo[1',5:1,6] pyrido [3 ,4-b] indo1e-2,3 -dicarboxylate.

7. A compound according to claim 1 wherein R represents cyclohexenyl.

8. A compound according to claim 1 which is dimethyl 10 (3 cyclohexenyl) 9,10 dihydro 4H pyrazolo- [1,5: 1,6 ]fpyrido [3,4-b indole-2,3 -dicarboxylate.

9. A compound according to claim 1 which is dimethyl 9,10 dihydro 1O phenyl 4H pyrazo1o[1',5':1,6] pyrido[3,4-b]indole-2,3-dicarboxylate.

10. A compound according to claim 1 wherein R represents halophenyl in which the halo constituent is chlorine or bromine.

11. A compound according to claim 1 which is dimethyl l0 (p chlorophenyl) 9,10 dihydro 4H pyrazolo- [1,5':1,6]pyrido[3,4-b]ind0le-2,3-dicarboxylate.

12. A compound according to claim 1 wherein R represents benzyl.

References Cited UNITED STATES PATENTS 3,299,078 1/1967 Pachter 260296 HENRY R. JILES, Primary Examiner ALAN L. ROTMAN, Assistant Examiner U.S. Cl. X.R. 

